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            <div><h3 class="title">
                <a name="asio.tutorial.tutdaytime2"></a><a class="link" href="tutdaytime2.html"
                                                           title="Daytime.2 - A synchronous TCP daytime server">Daytime.2
                - A synchronous
                TCP daytime server</a>
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    <p>
        This tutorial program shows how to use asio to implement a server application
        with TCP.
    </p>
    <pre class="programlisting"><span class="special">#</span><span class="identifier">include</span> <span
            class="special">&lt;</span><span class="identifier">ctime</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span
                class="identifier">iostream</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span
                class="identifier">string</span><span class="special">&gt;</span>
<span class="special">#</span><span class="identifier">include</span> <span class="special">&lt;</span><span
                class="identifier">asio</span><span class="special">.</span><span class="identifier">hpp</span><span
                class="special">&gt;</span>

<span class="keyword">using</span> <span class="identifier">asio</span><span class="special">::</span><span
                class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span
                class="special">;</span>
</pre>
    <p>
        We define the function <code class="computeroutput"><span class="identifier">make_daytime_string</span><span
            class="special">()</span></code> to create the string to be sent back to
        the client. This function will be reused in all of our daytime server applications.
    </p>
    <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span
            class="identifier">string</span> <span class="identifier">make_daytime_string</span><span
            class="special">()</span>
<span class="special">{</span>
  <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span
                class="special">;</span> <span class="comment">// For time_t, time and ctime;</span>
  <span class="identifier">time_t</span> <span class="identifier">now</span> <span class="special">=</span> <span
                class="identifier">time</span><span class="special">(</span><span class="number">0</span><span
                class="special">);</span>
  <span class="keyword">return</span> <span class="identifier">ctime</span><span class="special">(&amp;</span><span
                class="identifier">now</span><span class="special">);</span>
<span class="special">}</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
  <span class="keyword">try</span>
  <span class="special">{</span>
    <span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span> <span
                class="identifier">io_context</span><span class="special">;</span>
</pre>
    <p>
        A <a class="link" href="../reference/ip__tcp/acceptor.html" title="ip::tcp::acceptor">ip::tcp::acceptor</a>
        object needs to be created to listen for new connections. It is initialised
        to listen on TCP port 13, for IP version 4.
    </p>
    <pre class="programlisting">    <span class="identifier">tcp</span><span class="special">::</span><span
            class="identifier">acceptor</span> <span class="identifier">acceptor</span><span
            class="special">(</span><span class="identifier">io_context</span><span class="special">,</span> <span
            class="identifier">tcp</span><span class="special">::</span><span class="identifier">endpoint</span><span
            class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span
            class="identifier">v4</span><span class="special">(),</span> <span class="number">13</span><span
            class="special">));</span>
</pre>
    <p>
        This is an iterative server, which means that it will handle one connection
        at a time. Create a socket that will represent the connection to the client,
        and then wait for a connection.
    </p>
    <pre class="programlisting">    <span class="keyword">for</span> <span class="special">(;;)</span>
    <span class="special">{</span>
      <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span
                class="identifier">socket</span><span class="special">(</span><span class="identifier">io_context</span><span
                class="special">);</span>
      <span class="identifier">acceptor</span><span class="special">.</span><span class="identifier">accept</span><span
                class="special">(</span><span class="identifier">socket</span><span class="special">);</span>
</pre>
    <p>
        A client is accessing our service. Determine the current time and transfer
        this information to the client.
    </p>
    <pre class="programlisting">      <span class="identifier">std</span><span class="special">::</span><span
            class="identifier">string</span> <span class="identifier">message</span> <span
            class="special">=</span> <span class="identifier">make_daytime_string</span><span class="special">();</span>

      <span class="identifier">asio</span><span class="special">::</span><span
                class="identifier">error_code</span> <span class="identifier">ignored_error</span><span class="special">;</span>
      <span class="identifier">asio</span><span class="special">::</span><span class="identifier">write</span><span
                class="special">(</span><span class="identifier">socket</span><span class="special">,</span> <span
                class="identifier">asio</span><span class="special">::</span><span class="identifier">buffer</span><span
                class="special">(</span><span class="identifier">message</span><span class="special">),</span> <span
                class="identifier">ignored_error</span><span class="special">);</span>
    <span class="special">}</span>
  <span class="special">}</span>
</pre>
    <p>
        Finally, handle any exceptions.
    </p>
    <pre class="programlisting">  <span class="keyword">catch</span> <span class="special">(</span><span
            class="identifier">std</span><span class="special">::</span><span class="identifier">exception</span><span
            class="special">&amp;</span> <span class="identifier">e</span><span class="special">)</span>
  <span class="special">{</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span
                class="special">&lt;&lt;</span> <span class="identifier">e</span><span class="special">.</span><span
                class="identifier">what</span><span class="special">()</span> <span
                class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span
                class="identifier">endl</span><span class="special">;</span>
  <span class="special">}</span>

  <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
    <p>
        See the <a class="link" href="tutdaytime2/src.html" title="Source listing for Daytime.2">full source listing</a>
    </p>
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        Return to the <a class="link" href="../tutorial.html" title="Tutorial">tutorial index</a>
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    <p>
        Previous: <a class="link" href="tutdaytime1.html" title="Daytime.1 - A synchronous TCP daytime client">Daytime.1
        - A synchronous
        TCP daytime client</a>
    </p>
    <p>
        Next: <a class="link" href="tutdaytime3.html" title="Daytime.3 - An asynchronous TCP daytime server">Daytime.3 -
        An asynchronous
        TCP daytime server</a>
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